Start with household cash flow
Use take-home income and recurring obligations, including costs the purchase may add. Leave room for irregular bills instead of assigning every remaining dollar to debt.
Compare payment with total cost
A longer term can lower the monthly payment while increasing total interest. Review APR, fees, amount financed, number of payments, and total repayment together.
Stress-test the payment
Ask whether the payment still works after a temporary income drop or a common repair. If it depends on overtime or bonuses, model a lower-income case.
Example: a payment ceiling
If $900 remains after bills but the household needs $300 for irregular expenses and $200 for savings, the working payment ceiling is about $400—not the full $900.
What to check before you decide
- Affordability is personal and cannot be inferred from one debt ratio.
- Variable rates and balloon payments require different stress tests.
Sources behind this guide
These official and primary sources let you verify rules, definitions, and terms that may change.
CFPB — Financial terms glossary↗